Unusual F1 gearbox

[Nortonash]

I bought this F1 gearbox case many years ago without knowing anything about it. I dug it out from a pile of stuff this morning and decided it would be a good time to pick the brains of some of you guys. The difference is clear to anyone who is familiar with F1 gearboxes, the metal around the main bearing has been machined away and the bearing itself has a circlip midway on the outer race as opposed to close to the outer edge. I have absolutely no idea why it should have been altered in such a way. It still seems to be perfectly usuable as an F1 box.I do have some new bearings to fit which came with it so Norton obviously bought a few and maybe had bigger plans for the box ?

[Richard Negus]

Hi,That's one of the prototype gearcases for the F1-engined Commander. It was machined to allow fitment of a sprocket cover for the enclosed rear chain. One complete bike was made and there was second set of bits which were later made into a privately owned bike.With a suitable seal housing/bearing retainer, it should be ok for a normal F1 engine. You might find there are three bosses, tapped M8, underneath to take the Commander side stand bracket.R.

[Nortonash]

Hi Richard, thanks for that. There certainly doesnt look to be anything untoward that would affect it being used in an F1 as you say. Yes it does have 3 tapped holes on the bottom. Thanks again, hows things with you Richard ?

[Wayne]

Hi Asha picture o the whole box housing would be nice as i would like to see how the swininging arm bearings are seated, my interest is pure curiosity. I belive Grayham has a compleat f1 engined commander.Regards Wayne

[Richard Negus]

Wayne,I seem to remember that, like the F1, the bearings are in the rear fork and the spindle is fixed. I could be wrong, of course.R.

[Nortonash]

Hi Asha picture o the whole box housing would be nice as i would like to see how the swininging arm bearings are seated, my interest is pure curiosity. I belive Grayham has a compleat f1 engined commander.Regards Wayne

Hi Wayne, yes as Richard says the bearings are still in the swinging arm, the back of the gearbox is just standard but I will post a photo.

[Wayne]

Hi Allthe reason i asked, a commander gearbox has the left hand side machined away where the swingiing arm bearing is to fit the spondon race frame and the right hand side extended. the top bolt casting is cut off. I realy must try my f1 gearbox in the rc frames and my rc boxes in the f1 frame.I do have drawings on loan for a P55 wide center/big gearbox, Bob informs me the box was never made and is not the same as the race wide center gearbox. Its this wired one of stuff that can be a real headace if you dont have all of it, (as i have found to my cost. My P52 003 engine has some wired stuff going on thats definatly not standard. Then theres 666 rotors (someone at norton had a sence of humore) with stationary gears that can only be used with these rotors an vice versa. I know for a fact theres a pair of statoary gears knoking about because i did not buy them and only 25 sets were made along with the same amount of rotors. I have been told there was a gear driven primary engine but have not seen this, but i do have a aluminium F1 chain clutch drum thats been used, (then proberly regected infavour of the belt drive) so i suppose anythings possibleI am sure the gearbox pictured above will not be the last of weird and wonderfull stuff ash refinds in his collection

[Nortonash]

Wayne, here are a couple of photos for you. The top mount has been crudely chamfered as can be seen to persuade it into the frame I assume. The swingarm mount seems to be standard but I dont have my other gearbox handy to compare it to.

[Nortonash]

If you look closely at the bottom photo just to the right of the mount you will notice one of the threaded holes has been plugged by a Mud Wasp when it was on a shelf in Australia It is perfectly fine and washes out but it was a constant battle to stop them plugging every hole.

[Nortonash]

Sorry, cant edit posts, I meant the dowel hole to the left of the mount, doh.

[Richard Negus]

a commander gearbox has the left hand side machined away where the swingiing arm bearing is to fit the spondon race frame and the right hand side extended.Spondon frames and rear forks tend to be symmetrical about the bike's centre line. To get a wide enough chain line to suit race tyre widths, the engine had to be offset to the left; hence the pivot boss on the gearbox casting had to be shortened on the left and extended on the rightI have been told there was a gear driven primary engine but have not seen thisThat helical gear drive only existed as an arrangement drawing done by Doug Hele; it was anticipated that gear noise might be a problem so the design also allowed for a conventional chain drive. Renold came up with two simplex chains having a greater load capacity than a duplex and at a fraction of the cost. The idler gear was to run in needle bearings in the r/h plate and primary cover. Those castings were produced with bosses for the bearings, although they were machined off in the production engines.